<h3>
Answer: 6a^3-6a^2b+3ab-3b^2</h3>
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Work Shown:
(2a^2+b)(3a-3b)
c(3a-3b) ..... let c = 2a^2+b
3ac-3bc .... distribute
3a(c)-3b(c)
3a(2a^2+b)-3b(2a^2+b) .... plug in c = 2a^2+b
3a(2a^2)+3a(b)-3b(2a^2)-3b(b) ... distribute
6a^3+3ab-6a^2b-3b^2
6a^3-6a^2b+3ab-3b^2
You could also use the FOIL rule to get the same result. The box method is a visual way to keep track of the terms.
I'm pretty sure the answer is "19", but if i'm wrong please don't kill me.
a. First five terms: 9,13,17,21,25
b. Sum of first 25 terms = 1425
c. The given sequence is an arithmetic sequence because the common difference between two consecutive terms is same.
Further explanation:
Given
Formula of sequence

<u>1. First 5 terms:</u>
For first 5 terms, we have to put n=1,2,...5,
So,

<u>2. Sum of first 25 terms:</u>
For that we have to find 25th term first

The formula for sum is:

<u>3. Type of sequence</u>
The given sequence is an arithmetic sequence because the common difference between two consecutive terms is same.
i.e.

Keywords: Arithmetic sequence, Sum of arithmetic sequence
Learn more about arithmetic sequence at:
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